1. Field of the Invention
The present invention relates to a semiconductor device in which a series of semiconductor chips are electrically connected to each other, and, more particularly, are incorporated to apparatus as such as an image reader wherein semiconductor chips are incorporated to convert information on a document into an electrical signal, or a thermal printer wherein semiconductor chips are incorporated to thermally convert image information and record an image onto a recording medium.
2. Description of the Related Art
Conventionally, semiconductor chips have been incorporated in an image reader and a thermal print head. In the conventional image reader, an image on a document is formed in a photo-converting section by a lens system, thereby reading information on the document. However, there is a growing need for equipment that can read a large-sized document. Particularly, an image reader, which can sufficiently read the document as large as A4-sized or B4-sized documents, has been required. Such a technique has been also required in the recording apparatus such as a thermal print head as well as the reader.
For example, Japanese Patent Application No. 62-31159 discloses a reader in which a plurality of semiconductor chips having a photo-converting section are connected by bonding wires in a direction where photo-converting elements are arranged. According to such a reader, the large-sized documents can be sufficiently read.
However, if the rod lens, such as SELFOC lens, is provided between the document and the photo-converting section, the size of the apparatus is necessarily enlarged. For this reason, there has recently been considered a reader from which the optical system is removed, that is, the reader wherein a photo-converting section having the same size as a document is disposed closer to the document and information on the document is read. In other words, in the above-structured reader, in view of the improvement of reading accuracy, it is preferable to place the document close to the photo-converting section at substantially 50 .mu.m to read information on the document.
However, if the document is placed closer to the photo-converting section to improve the reading accuracy, bonding wires, which are used to connect the chips having the photoelectric converting section, come near the document and the photo-converting section, thereby preventing the document from being transferred or causing the breakage of the bonding wires.
In order to allow the chips to be connected in the region other than the region where the document and the photo-converting section are placed closer to each other, each chip is enlarged in a sub-scanning direction. Thereby, making it possible to prevent the document from being transferred by the bonding wires.
However enlarging the respective chips in the sub-scanning direction increases not only the size of the apparatus but also the manufacturing cost of the apparatus. Particularly, it has been required that the width of the chip be less than 1 mm to obtain the low manufacturing cost of the apparatus by forming a large number of chips out of one substrate.